Jens Keller, the interim coach of Schalke, could hardly face a more daunting Champions League debut when his team visit Galatasaray for the first leg of their last-16 tie on Wednesday.

Keller was supposed to halt Schalke's mid-season slump but he has succeeded in gaining only one win from six games in all competitions since taking over from the dismissed Huub Stevens in December.

Altogether Schalke have only one win from 12 games, and their unbeaten record in the Champions League this season faces a stiff test against a Galatasaray side bolstered by the recent signings of Didier Drogba and Wesley Sneijder.

Drogba, who won the competition with Chelsea last year after equalising in the game and scoring the decisive penalty in their shootout with Bayern Munich, scored a spectacular header five minutes into his debut at Galatasaray on Friday, in a move instigated by Sneijder, a 2010 Champions League winner with Internazionale. "Both of them have quickly merged and integrated with the team," the Galatasaray coach, Fatih Terim, said.

The Turkish champions have recovered from a poor start in the Champions League and strung together three successive wins to finish second behind Manchester United in Group H. They also lead the Turkish league by six points – with five wins from their last eight games – in sharp contrast to Schalke, who have tumbled from second to ninth in the Bundesliga.

The Gelsenkirchen-based club had Michel Bastos to thank for salvaging a 2-2 draw at Mainz on Saturday, when the Brazilian scored twice to make it three goals in as many games since his recent transfer from Lyon. "That was important," Bastos said later. His late goal provided breathing space for Keller, whose melancholy demeanour has not instilled confidence, and who spoke before the game of "a curse" affecting his side.

But his side will be boosted by Huntelaar's return for the game in Istanbul. The Holland striker has been passed fit to play after recovering from a ruptured vein in his left eye.

"I had no problems in training and am ready for Istanbul," Huntelaar said. "I feel good and can see everything."

With only five goals in the Bundesliga so far this season, the Dutchman has not shone, but he has four from six Champions League games and the team are counting on his experience.

"It's important that the 'Hunter' is fit again," said Marco Höger, who will play at right-back in place of Uchida, a hamstring-injury victim. Afellay (muscle tear), Marica (meniscus) and Moritz (torn ankle ligaments) also remain unavailable, while the defender Papadopoulos and goalkeeper Unnerstall are both recovering from knee operations.

Raffael is ineligible after playing for Dynamo Kyiv in the competition already this season. Bastos can play as Lyon only took part in the Europa League, however.

The buildup has been dominated by speculation linking the Bayern Munich coach Jupp Heynckes with the job at Schalke next season.

"This is the usual madness. We have to live with it. It doesn't affect the preparations," said the Schalke sports director, Horst Heldt, who believes a good result in Istanbul could help kickstart a recovery and help them back to the promising form they showed at the beginning of the season.

"We are one of four teams unbeaten in the Champions League [this season]. It would be nice if it stayed that way. It won't be easy. It'll be another notch louder in the stadium that it was in Piraeus," he added, referring to Schalke's 2-1 win over Olympiakos in the opening group game. "It's important for the upcoming tasks in the Bundesliga to build up strength and morale with a good game at Galatasaray."

One familiar face awaits the Germans in Istanbul. The Galatasaray midfielder Hamit Altintop was born in Gelsenkirchen and played for Schalke from 2003-07, scoring eight goals and setting up 11 more in 113 league appearances before switching to Bayern. Altintop, who joined Galatasaray from Real Madrid last year, warned his new team-mates that "Schalke will play with great discipline".

"We don't need to be afraid," Schalke's captain, Benedikt Höwedes, said. "A cauldron awaits us, but these are also games you have to look forward to."

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